Vitamin B12 plays an important role in synthesising and metabolising serotonin, a chemical responsible for regulating mood.
Research supports the use of vitamin B12 supplements for alleviating symptoms of depression in people deficient in the vitamin. One study in people with depression and low vitamin B12 levels indicated that those who received both antidepressants and vitamin B12 were more likely to display improved depressive symptoms, compared to those provided antidepressants alone. (20)
Another study established that vitamin B12 deficiency was associated with double the risk of severe depression. (21)